His HBO show starts slow, but his views of mortality are more funny and his fixation on 'horrible thoughts' still more so. Still, it's no 'Louie.'

It is heartening in a way that perhaps the biggest comic in America — in a sense of cultural import if not necessarily in income, though he is obviously doing well there too — is a doughy, bald man of 45. It's heartening both from the aspect of one's own advancing age and as notice that kids these days are not entirely consumed with things made in their own image.

That experience counts for something is an explicitly stated theme of Louis C.K.'s new concert special, "Oh My God," which premieres Saturday on HBO: Real wisdom is a thing that only time can earn, he says. Of course, he also talks about how leaning over to put his socks on is "like folding a bowling ball in half" and that getting up out of a chair resembles "trying to get an old Honda out of a snowbank." More to the point, it involves him first asking the question, "Do I really want to be alive anymore?"

Though C.K. has been interesting for a long time, a morally ambitious comic with smart things to say offstage about his metier, it isn't surprising that his rise in status and stature has come alongside his brilliant FX series, "Louie." Because it embodies ideas — Louie, the character, is surrounded by other humans, who get to have their say — it's a vehicle more responsive to his ideas and sensibilities, delicate and brutal, than the stage, with its apparent absolute freedom to say anything, at length.

Still, it is good to see him leading this trip. Formally, there is not much space between the stand-up comic and the preacher; both are entertainers, both are concerned with truth, sometimes at the expense of facts; both seek to liberate their audience from old patterns of seeing. The lesser ones want you to think like them; but the greatest just want to break open your mind.

If the club circuit embodies a kind of trench warfare, where the comedian advances joke by joke under the fire of his audience, the concert stage is something else — a celebration of success. And while this mitigates failure and grants permission to wander where one will, it is also a strange place for a professional gadfly to find himself. The court jester was always a word away from decapitation, but the beloved comic is almost a king. It takes discipline not to cross that line.

The first quarter of "Oh My God," much of which is taken with making fun of animals, is oddly conservative. It feels easy and superior and a little wrong-headed. (Watching, I sweated the sweat of fretful fanship; I wanted C.K. to do well, but I also wanted to feel confirmed in my overall love for his work.) The first time I laughed out loud was when the comic spilled water on himself, because it suddenly made things real, bringing what is, after all, a highly crafted presentation, into the moment — spontaneously spontaneous, and not just theatrically so.

As with much comedy today, and some comedy always, sex is never far out of the picture, though C.K. is less interested in telling dirty jokes than in examining primal urges and what keeps us from expressing them publicly — these include a man's impulse to feel a woman's breasts; yelling at people in elevators the way you yell at them while driving ("I like to think I'm a nice person," he says, "but I don't know — a lot of it is context"); and, taking it to the limit, murdering one's children.

"That is a whole bunch of horrible thoughts right in a row," he says at one point.

The show, as it should, gets stronger as it goes on, and the last minutes run headlong into the horrible thoughts. A riff on progress and suffering and human history that brings the crowd into the equation is ingenious and powerful and, this being the indispensable point, funny.

For all his darkness, C.K. is a friendly performer; he smiles a lot onstage; he seems happy and declares himself so. (Divorce, he tells us, is good.) But when he finishes, to rapturous applause, the air seems to go out of him a bit.

He acknowledges the love of the crowd but doesn't bask in it and leaves the stage not in giddy triumph but soberly, having survived another turn on the wheel of fire.